Drive mechanism for a drug delivery device The present invention relates to a drive mechanism for a drug delivery device as well as to a drug delivery device for dispensing of a dose of a medicinal product, wherein the drive mechanism comprises: a holder (14) for a product-containing cartridge (16), the cartridge (16) having a piston (18) slidably arranged therein in an axial direction, a piston rod (26； 48； 52； 62； 76； 92； 116) to be operably engaged with the cartridge's piston (18) for dispensing of a dose of the medicinal product, - at least one adjusting member (20； 46； 54； 64； 78； 90； 112) slidably arranged in axial direction relative to the piston (18) and/or relative to the piston rod (26； 48； 52； 62； 76； 92； 116) for eliminating axial clearance (34) between th piston (18) and the piston rod (26； 48； 52； 62； 76； 92； 116), - an interlock means (24； 58； 66； 80； 100) adapted to interact with the adjusting member (20； 46； 54； 64； 78； 90； 112) for mutually locking in position the piston (18) and the piston rod (26； 48； 52； 62； 76； 92； 116) irrespective of the relative distance between piston (18) and piston rod (26； 48； 52； 62； 76； 92； 116).
